1. Field of the Invention
The invention relates to a pneumatic vehicle tire in radial construction having a carcass and having components adjoining the carcass, and thread-shaped elements arranged on at least one of the two surfaces of the carcass, which are provided for discharge of enclosed air between the carcass and the adjoining components during the tire construction. The invention also relates to a method for producing an electrically conductive coating for the thread-shaped elements.
2. Discussion of Background Information
Radial tires having thread-shaped elements for air discharge (so-called “air-discharging threads”) are sufficiently known to a person skilled in the art. Such a pneumatic vehicle tire is known, for example, from DE 3 014 268 A1. Radial tires are distinguished by a radial extension of the carcass reinforcement. The carcass is produced in a textile calender, in that the inlay is coated using a mixture layer made of rubber.
In order to prevent air from being enclosed between components joined to one another during tire construction, and therefore, the quality of the tire from being decreased, the carcass component is covered after its production in the textile calender on the surface of the mixture layer using thread-shaped elements, which are arranged parallel to one another, for air discharge. This covering can be performed on one side, i.e., on only one of the two surfaces of the carcass, or on both sides or both surfaces of the carcass. The covering using the thread-shaped air-discharging elements, which are not electrically conductive or are inadequately electrically conductive, is typically performed at an interval of 25 to 40 mm. The air-discharging elements are, for example, cotton threads having a diameter of 0.05-1 mm. In the tire, the thread-shaped elements for air discharge extend in the radial direction and span the entire carcass layer width.
To be able to dissipate the electrostatic charge occurring during operation of the tire, the head region, which comes into contact with the roadway surface and includes treads, the bead region, which comes into contact with the tire rim, and at least one component, such as an inner layer, a carcass, or a side wall, which connects the tread and the bead region to one another, are made electrically conductive. This can be performed, for example, through the use of electrically conductive rubber mixtures. Electrically conductive means that the tire has an electrical resistance of at most 1×108 ohm.
Development is now directed to reducing the rolling resistance of the tire. One approach for reducing the rolling resistance is the use of low-rolling-resistance mixtures. They are preferably used as so-called “body mixtures” in the side wall region, for the inner layer and for the carcass. The hysteresis of these low-rolling-resistance mixtures may be decreased above all through the use of less-active fillers, smaller quantities of filler, or by replacing carbon black with silica. Thus, the use of these low-rolling-resistance mixtures results in an increase of the electrical resistance of these mixtures, however, so that the electrical conductivity drops. The required electrical resistance of the overall tire of 1×108 ohm to dissipate the electrostatic charge cannot be ensured.
So-called conductive carbon blacks are often used in ultralow concentrations in the above-mentioned components as a remedy. However, these have a very high reinforcing/stiffening effect and also have a negative effect on the hysteresis behavior and therefore the rolling resistance. So as not to exceed a required low stiffness of a mixture, e.g., in the side wall region, the degree of filling with other reinforcing fillers must be substantially reduced as a compensation for the conductive carbon blacks. In soft components such as the side wall, this can have the result that the total degree of filling is very low. As a consequence, a dispersion of the conductive carbon blacks, which have a high surface area, is no longer satisfactorily possible, with the disadvantages of excessively low strength or abrasion resistance, for example. In addition, such a measure based on conductive carbon blacks is costly.